Re: [PATCH V8 4/5] libsas: Align SMP req/resp todma_get_cache_alignment()

From: éåæ
Date: Tue Oct 17 2017 - 21:13:10 EST

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Hi, Marek,

Yes, I know in include/linux/slab.h, there is
#define KMALLOC_MIN_SIZE ARCH_DMA_MINALIGN

But I observed that the req/resp isn't aligned to ARCH_DMA_MINALIGN and I don't know why.

Problems I experienced is: In non-coherent mode, mvsas with an expander cannot detect any disks.

Huacai

------------------ Original ------------------
From: "Marek Szyprowski"<m.szyprowski@xxxxxxxxxxx>;
Date: Tue, Oct 17, 2017 07:55 PM
To: "Huacai Chen"<chenhc@xxxxxxxxxx>; "Christoph Hellwig"<hch@xxxxxx>;
Cc: "Robin Murphy"<robin.murphy@xxxxxxx>; "Andrew Morton"<akpm@xxxxxxxxxxxxxxxxxxxx>; "Fuxin Zhang"<zhangfx@xxxxxxxxxx>; "linux-kernel"<linux-kernel@xxxxxxxxxxxxxxx>; "Ralf Baechle"<ralf@xxxxxxxxxxxxxx>; "JamesHogan"<james.hogan@xxxxxxxxxx>; "linux-mips"<linux-mips@xxxxxxxxxxxxxx>; "James E . J .Bottomley"<jejb@xxxxxxxxxxxxxxxxxx>; "Martin K . Petersen"<martin.petersen@xxxxxxxxxx>; "linux-scsi"<linux-scsi@xxxxxxxxxxxxxxx>; "Tejun Heo"<tj@xxxxxxxxxx>; "linux-ide"<linux-ide@xxxxxxxxxxxxxxx>; "stable"<stable@xxxxxxxxxxxxxxx>;
Subject: Re: [PATCH V8 4/5] libsas: Align SMP req/resp todma_get_cache_alignment()

Hi Huacai,

On 2017-10-17 10:05, Huacai Chen wrote:
> In non-coherent DMA mode, kernel uses cache flushing operations to
> maintain I/O coherency, so libsas's SMP request/response should be
> aligned to ARCH_DMA_MINALIGN. Otherwise, If a DMA buffer and a kernel
> structure share a same cache line, and if the kernel structure has
> dirty data, cache_invalidate (no writeback) will cause data corruption.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Huacai Chen <chenhc@xxxxxxxxxx>
> ---
> drivers/scsi/libsas/sas_expander.c | 93 +++++++++++++++++++++++---------------
> 1 file changed, 57 insertions(+), 36 deletions(-)
>
> diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
> index 6b4fd23..124a44b 100644
> --- a/drivers/scsi/libsas/sas_expander.c
> +++ b/drivers/scsi/libsas/sas_expander.c
> @@ -164,17 +164,17 @@ static int smp_execute_task(struct domain_device *dev, void *req, int req_size,
>
> /* ---------- Allocations ---------- */
>
> -static inline void *alloc_smp_req(int size)
> +static inline void *alloc_smp_req(int size, int align)
> {
> - u8 *p = kzalloc(size, GFP_KERNEL);
> + u8 *p = kzalloc(ALIGN(size, align), GFP_KERNEL);

If I remember correctly, kernel guarantees that each kmalloced buffer is
always at least aligned to the CPU cache line, so CPU cache can be
invalidated on the allocated buffer without corrupting anything else.
Taking this into account, I wonder if the above change make sense.

Have you experienced any problems without this change?

> if (p)
> p[0] = SMP_REQUEST;
> return p;
> }
>
> -static inline void *alloc_smp_resp(int size)
> +static inline void *alloc_smp_resp(int size, int align)
> {
> - return kzalloc(size, GFP_KERNEL);
> + return kzalloc(ALIGN(size, align), GFP_KERNEL);

Save a above.

> }
>
> static char sas_route_char(struct domain_device *dev, struct ex_phy *phy)
> @@ -403,15 +403,17 @@ static int sas_ex_phy_discover_helper(struct domain_device *dev, u8 *disc_req,
> int sas_ex_phy_discover(struct domain_device *dev, int single)
> {
> struct expander_device *ex = &dev->ex_dev;
> - int res = 0;
> + int res = 0, align;
> u8 *disc_req;
> u8 *disc_resp;
>
> - disc_req = alloc_smp_req(DISCOVER_REQ_SIZE);
> + align = dma_get_cache_alignment(&dev->phy->dev);
> +
> + disc_req = alloc_smp_req(DISCOVER_REQ_SIZE, align);
> if (!disc_req)
> return -ENOMEM;
>
> - disc_resp = alloc_smp_resp(DISCOVER_RESP_SIZE);
> + disc_resp = alloc_smp_resp(DISCOVER_RESP_SIZE, align);
> if (!disc_resp) {
> kfree(disc_req);
> return -ENOMEM;
> @@ -480,14 +482,15 @@ static int sas_ex_general(struct domain_device *dev)
> {
> u8 *rg_req;
> struct smp_resp *rg_resp;
> - int res;
> - int i;
> + int i, res, align;
>
> - rg_req = alloc_smp_req(RG_REQ_SIZE);
> + align = dma_get_cache_alignment(&dev->phy->dev);
> +
> + rg_req = alloc_smp_req(RG_REQ_SIZE, align);
> if (!rg_req)
> return -ENOMEM;
>
> - rg_resp = alloc_smp_resp(RG_RESP_SIZE);
> + rg_resp = alloc_smp_resp(RG_RESP_SIZE, align);
> if (!rg_resp) {
> kfree(rg_req);
> return -ENOMEM;
> @@ -552,13 +555,15 @@ static int sas_ex_manuf_info(struct domain_device *dev)
> {
> u8 *mi_req;
> u8 *mi_resp;
> - int res;
> + int res, align;
>
> - mi_req = alloc_smp_req(MI_REQ_SIZE);
> + align = dma_get_cache_alignment(&dev->phy->dev);
> +
> + mi_req = alloc_smp_req(MI_REQ_SIZE, align);
> if (!mi_req)
> return -ENOMEM;
>
> - mi_resp = alloc_smp_resp(MI_RESP_SIZE);
> + mi_resp = alloc_smp_resp(MI_RESP_SIZE, align);
> if (!mi_resp) {
> kfree(mi_req);
> return -ENOMEM;
> @@ -593,13 +598,15 @@ int sas_smp_phy_control(struct domain_device *dev, int phy_id,
> {
> u8 *pc_req;
> u8 *pc_resp;
> - int res;
> + int res, align;
> +
> + align = dma_get_cache_alignment(&dev->phy->dev);
>
> - pc_req = alloc_smp_req(PC_REQ_SIZE);
> + pc_req = alloc_smp_req(PC_REQ_SIZE, align);
> if (!pc_req)
> return -ENOMEM;
>
> - pc_resp = alloc_smp_resp(PC_RESP_SIZE);
> + pc_resp = alloc_smp_resp(PC_RESP_SIZE, align);
> if (!pc_resp) {
> kfree(pc_req);
> return -ENOMEM;
> @@ -664,17 +671,19 @@ static int sas_dev_present_in_domain(struct asd_sas_port *port,
> #define RPEL_RESP_SIZE 32
> int sas_smp_get_phy_events(struct sas_phy *phy)
> {
> - int res;
> + int res, align;
> u8 *req;
> u8 *resp;
> struct sas_rphy *rphy = dev_to_rphy(phy->dev.parent);
> struct domain_device *dev = sas_find_dev_by_rphy(rphy);
>
> - req = alloc_smp_req(RPEL_REQ_SIZE);
> + align = dma_get_cache_alignment(&phy->dev);
> +
> + req = alloc_smp_req(RPEL_REQ_SIZE, align);
> if (!req)
> return -ENOMEM;
>
> - resp = alloc_smp_resp(RPEL_RESP_SIZE);
> + resp = alloc_smp_resp(RPEL_RESP_SIZE, align);
> if (!resp) {
> kfree(req);
> return -ENOMEM;
> @@ -709,7 +718,8 @@ int sas_get_report_phy_sata(struct domain_device *dev, int phy_id,
> struct smp_resp *rps_resp)
> {
> int res;
> - u8 *rps_req = alloc_smp_req(RPS_REQ_SIZE);
> + int align = dma_get_cache_alignment(&dev->phy->dev);
> + u8 *rps_req = alloc_smp_req(RPS_REQ_SIZE, align);
> u8 *resp = (u8 *)rps_resp;
>
> if (!rps_req)
> @@ -1398,7 +1408,7 @@ static int sas_check_parent_topology(struct domain_device *child)
> static int sas_configure_present(struct domain_device *dev, int phy_id,
> u8 *sas_addr, int *index, int *present)
> {
> - int i, res = 0;
> + int i, res = 0, align;
> struct expander_device *ex = &dev->ex_dev;
> struct ex_phy *phy = &ex->ex_phy[phy_id];
> u8 *rri_req;
> @@ -1406,12 +1416,13 @@ static int sas_configure_present(struct domain_device *dev, int phy_id,
>
> *present = 0;
> *index = 0;
> + align = dma_get_cache_alignment(&dev->phy->dev);
>
> - rri_req = alloc_smp_req(RRI_REQ_SIZE);
> + rri_req = alloc_smp_req(RRI_REQ_SIZE, align);
> if (!rri_req)
> return -ENOMEM;
>
> - rri_resp = alloc_smp_resp(RRI_RESP_SIZE);
> + rri_resp = alloc_smp_resp(RRI_RESP_SIZE, align);
> if (!rri_resp) {
> kfree(rri_req);
> return -ENOMEM;
> @@ -1472,15 +1483,17 @@ static int sas_configure_present(struct domain_device *dev, int phy_id,
> static int sas_configure_set(struct domain_device *dev, int phy_id,
> u8 *sas_addr, int index, int include)
> {
> - int res;
> + int res, align;
> u8 *cri_req;
> u8 *cri_resp;
>
> - cri_req = alloc_smp_req(CRI_REQ_SIZE);
> + align = dma_get_cache_alignment(&dev->phy->dev);
> +
> + cri_req = alloc_smp_req(CRI_REQ_SIZE, align);
> if (!cri_req)
> return -ENOMEM;
>
> - cri_resp = alloc_smp_resp(CRI_RESP_SIZE);
> + cri_resp = alloc_smp_resp(CRI_RESP_SIZE, align);
> if (!cri_resp) {
> kfree(cri_req);
> return -ENOMEM;
> @@ -1689,10 +1702,12 @@ int sas_discover_root_expander(struct domain_device *dev)
> static int sas_get_phy_discover(struct domain_device *dev,
> int phy_id, struct smp_resp *disc_resp)
> {
> - int res;
> + int res, align;
> u8 *disc_req;
>
> - disc_req = alloc_smp_req(DISCOVER_REQ_SIZE);
> + align = dma_get_cache_alignment(&dev->phy->dev);
> +
> + disc_req = alloc_smp_req(DISCOVER_REQ_SIZE, align);
> if (!disc_req)
> return -ENOMEM;
>
> @@ -1715,10 +1730,12 @@ static int sas_get_phy_discover(struct domain_device *dev,
> static int sas_get_phy_change_count(struct domain_device *dev,
> int phy_id, int *pcc)
> {
> - int res;
> + int res, align;
> struct smp_resp *disc_resp;
>
> - disc_resp = alloc_smp_resp(DISCOVER_RESP_SIZE);
> + align = dma_get_cache_alignment(&dev->phy->dev);
> +
> + disc_resp = alloc_smp_resp(DISCOVER_RESP_SIZE, align);
> if (!disc_resp)
> return -ENOMEM;
>
> @@ -1733,11 +1750,13 @@ static int sas_get_phy_change_count(struct domain_device *dev,
> static int sas_get_phy_attached_dev(struct domain_device *dev, int phy_id,
> u8 *sas_addr, enum sas_device_type *type)
> {
> - int res;
> + int res, align;
> struct smp_resp *disc_resp;
> struct discover_resp *dr;
>
> - disc_resp = alloc_smp_resp(DISCOVER_RESP_SIZE);
> + align = dma_get_cache_alignment(&dev->phy->dev);
> +
> + disc_resp = alloc_smp_resp(DISCOVER_RESP_SIZE, align);
> if (!disc_resp)
> return -ENOMEM;
> dr = &disc_resp->disc;
> @@ -1787,15 +1806,17 @@ static int sas_find_bcast_phy(struct domain_device *dev, int *phy_id,
>
> static int sas_get_ex_change_count(struct domain_device *dev, int *ecc)
> {
> - int res;
> + int res, align;
> u8 *rg_req;
> struct smp_resp *rg_resp;
>
> - rg_req = alloc_smp_req(RG_REQ_SIZE);
> + align = dma_get_cache_alignment(&dev->phy->dev);
> +
> + rg_req = alloc_smp_req(RG_REQ_SIZE, align);
> if (!rg_req)
> return -ENOMEM;
>
> - rg_resp = alloc_smp_resp(RG_RESP_SIZE);
> + rg_resp = alloc_smp_resp(RG_RESP_SIZE, align);
> if (!rg_resp) {
> kfree(rg_req);
> return -ENOMEM;

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Next message: Ming Lei: "Re: [PATCH 0/2] block/SCSI MQ: two RESTART related patches"
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In reply to: Marek Szyprowski: "Re: [PATCH V8 4/5] libsas: Align SMP req/resp to dma_get_cache_alignment()"
Next in thread: Christoph Hellwig: "Re: [PATCH V8 4/5] libsas: Align SMP req/resp to dma_get_cache_alignment()"
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